1. Field of the Invention
The present invention generally relates to a cylinder identifying system for an internal combustion engine mounted on an automobile or a motor vehicle. More particularly, the present invention is concerned with a cylinder identifying system for an internal combustion engine which system is designed for identifying discriminatively individual cylinders of the internal combustion engine within a short time even upon starting of the engine operation and changing of valve timing for thereby enhancing control performance.
2. Description of Related Art
As the hitherto known or conventional cylinder identifying system using, for example, a crank angle pulse signal and a cam pulse signal in the internal combustion engine which is equipped with a variable valve timing mechanism (hereinafter also referred to as the VVT mechanism), there may be mentioned the one which is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 224620/1995 (JP-A-7-224620).
In the cylinder identifying system described in the publication mentioned above, a reference position given in terms of the a crank angle is detected on the basis of a crank angle pulse signal containing a reference signal. A given or specific cylinder can be determined discriminatively or identified by detecting presence/absence of a cam signal pulse in a particular or specific period succeeding to the detection of the reference position.
In this case, the cam signal pulse for cylinder identification is so set as to be generated or outputted three times for one rotation of a cam shaft (corresponding to two rotations of a crank shaft) in consideration of the controllability of the variable valve timing for the reason described below.
When the number of times the cam signal pulse is outputted is set to once for two rotations of the crank shaft, the VVT signal phase can be detected only once during two revolutions of the engine, incurring degradation of phase control performance of the VVT mechanism.
On the other hand, when the number of times the cam signal pulses are outputted is set to four times or more for two revolutions of the engine, deviation in the angular position of the cam pulse signal relative to the crank angle pulse signal will take place under the influence of change of the valve drive timing phase variable range due to the variable valve timing control, which incurs erroneous identification of the cylinder, to great disadvantage.
More specifically, in the conventional cylinder identifying system described in the above publication, when the valve drive timing phase changes due to the variable valve timing control, the cylinder identification is performed within a specific angular range of the crank angle pulse signal. Thus, a cam signal pattern for the cylinder identification is of a relatively simple structure.
However, in the cylinder identification, presence or absence of the cam signal pulse is determined discriminatively after detection of the reference signal from the crank angle pulse signal. Accordingly, when the detection of the crank angle pulse signal is started immediately after the detection of the reference signal, the reference signal can not be detected (i.e., the cylinder identification can not be started, to say in another way) without detecting the crank angle pulse signal after about one revolution of the engine.
As will now be understood from the foregoing description, in the conventional cylinder identifying system for the internal combustion engine, the cylinder identification is performed within a predetermined range of crank angle without taking into account the change of the cam pulse signal phase brought about through the variable valve timing control. Further, the cylinder identification is performed after detection of the reference signal on the basis of presence/absence of the cam pulse signal by referencing a relatively simple cam signal pulse pattern. Consequently, in the worst case where the signal detection is started immediately succeeding to the reference signal, one or more revolutions of the engine is required for completing the cylinder identification, giving rise to a problem that the engine control performance will be degraded.
In the light of the state of the art described above, it is an object of the present invention to provide a cylinder identifying system for an internal combustion engine which system is capable of establishing a complicated cam signal pattern without need for setting any particular or specific periods for the purpose of cylinder identification for thereby enhancing the engine control performance by reducing a engine revolution quantity required for the cylinder identification.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a cylinder identifying system for an internal combustion engine, which system includes a crank angle signal generating means provided in association with a crank shaft of the internal combustion engine for generating a crank angle pulse signal in synchronization with rotation of the crank shaft of the engine, a cam signal generating means provided in association with a cam shaft for generating a cam pulse signal containing specific pulses for identifying individual cylinders of the internal combustion engine in synchronization with rotation of the cam shaft rotating at a speed corresponding to one half of that of the crank shaft, a variable valve timing means for setting variably phase of valve drive timing for the individual cylinders, respectively, in dependence on operating states of the engine, and a cylinder identifying means designed for operating in synchronization with the phase of the valve drive timing for the individual cylinders which is changed by the variable valve timing means, for thereby identifying discriminatively the individual cylinders on the basis of the crank angle pulse signal and the cam pulse signal. In the cylinder identifying system mentioned above, the cylinder identifying means is comprised of a pulse signal number storage means for counting for storage signal numbers of the specific pulses generated over a plurality of subperiods which are defined by dividing an ignition control period for each of the individual cylinders into plural subperiods, and an information series storage means for storing information series composed of a combination of the signal numbers of the specific phases generated during the plural subperiods, respectively, wherein the individual cylinders of the internal combustion engine are identified on the basis of the information series.
By virtue of the arrangement described above, there is provided for an internal combustion engine the cylinder identifying system which is capable of setting a complicated cam pulse signal patterns without need for establishing any particular periods for the cylinder identification and which can decrease the angle of rotation required for the cylinder identification, to thereby allow the engine controllability to be enhanced and improved significantly.
In a preferred mode for carrying out the invention, the information series may be composed of four successive signals containing the specific pulses.
Owing to the feature described above, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced.
In another preferred mode for carrying out the invention, the information series storage means may be so designed as to store a plurality of information series which are variable within a range in which the phase of the valve drive timing is changed by the variable valve timing means. The cylinder identifying means may preferably be so designed as to identify a given one of the cylinders on the basis of at least one of the plural information series.
With the arrangement described above, even when the phase of the cam pulse signal is advanced due to the variable valve timing control, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced.
In yet another preferred mode for carrying out the invention, the cylinder identifying means may be comprised of an information series learning means for learning a first one of the information series at a predetermined crank angle based on the crank angle pulse signal, wherein the cylinder identifying means may be so arranged as to identify the individual cylinders on the basis of a result of comparison of the information series detected currently with the first information series learned.
In still another preferred mode for carrying out the invention, the cylinder identifying means may be comprised of a changeable information series arithmetic means for determining arithmetically a second one of the information series which can vary within a range of the predetermined crank angle on the basis of the first information series and the range within which the phase of the valve drive timing can be changed by means of the variable valve timing means, wherein the cylinder identifying means is so arranged as to identify the individual cylinders, respectively, on the basis of result of comparison between the information series detected currently and at least one of the first and second information series.
In a further preferred mode for carrying out the invention, the information series learning means may be so arranged as to learn the first information series at a time point which corresponds to at least one of a most retarded valve drive timing and a most advanced valve drive timing set by the variable valve timing means.
In a yet further preferred mode for carrying out the invention, the information series learning means may be so arranged as to learn the first information series at a time point at which operation of the internal combustion engine is started.
Owing to the arrangements of the cylinder identifying system described above, even when the sensor mounting error should occur and/or even when the phase of the cam pulse signal is advanced due to the variable valve timing control, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced.
In a still further preferred mode for carrying out the invention, the crank angle pulse signal may be comprised of pulse trains each containing a pulse indicative of a reference position for each of the individual cylinders, wherein the plural subperiods are established by dividing the ignition control period with reference to the reference position.
Owing to the feature described above, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced.
In another preferred mode for carrying out the invention, the cylinder identifying means may be so arranged as to identify the individual cylinders at least either during a predetermined time period from a time point at which the engine operation is started or at a time point corresponding to the most retarded valve drive timing set by the variable valve timing means.
By virtue of the arrangement described above, even when the amount of the stored information series data is small, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced.
In yet another preferred mode for carrying out the invention, the cylinder identifying system for the internal combustion may further include a phase detecting means for detecting a change of the valve drive timing phase shifted by means of the variable valve timing means on the basis of given specific pulses contained in the cam pulse signal and crank angle position information derived from the crank angle pulse signal.
With the arrangement described above, the angle of rotation required for the cylinder identification can be decreased, whereby the engine operation controllability can be enhanced. Furthermore, high freedom in design as well as cost reduction can be realized.
In still another preferred mode for carrying out the invention which is applied to a four-cylinder internal combustion engine in which the ignition control period for each of the cylinders may be so set as to correspond to a crank angle of 180xc2x0, the plural subperiods corresponding to each of the individual cylinders should be comprised of a first subperiod and a second subperiod, respectively, wherein the numbers of the specific pulses contained in the cam pulse signal generated during the first subperiod and the second subperiod, respectively, should be xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d; xe2x80x9c2xe2x80x9d and xe2x80x9c1xe2x80x9d; xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d; and xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the sequential order in which the cylinders are controlled.
With the arrangement described above, the angle of rotation required for cylinder identification of the four-cylinder engine can be decreased, whereby engine operation controllability can be enhance.
In a further preferred mode for carrying out the invention applied to a six-cylinder internal combustion engine in which the ignition control period for each of the cylinders is so set as to correspond to a crank angle of 120xc2x0, the plural subperiods corresponding to the individual cylinders should be comprised of a first subperiod and a second subperiod, respectively, wherein the numbers of the specific pulses contained in the cam pulse signal generated during the first subperiod and the second subperiod, respectively, should be xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d; xe2x80x9c2xe2x80x9d and xe2x80x9c0xe2x80x9d; xe2x80x9c1xe2x80x9d and xe2x80x9c2xe2x80x9d; xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d; xe2x80x9c1xe2x80x9d and xe2x80x9c1xe2x80x9d; and xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the sequential order in which the cylinders are controlled.
Owing to the arrangement described above, the angle of rotation required for cylinder identification of the six-cylinder engine can be decreased, whereby engine operation controllability can be enhance.
In a yet further preferred mode for carrying out the invention applied to a three-cylinder internal combustion engine in which the ignition control period for each of the cylinders is so set as to correspond to a crank angle of 240xc2x0, the plural subperiods should be comprised of a first subperiod, a second subperiod, a third subperiod and a fourth subperiod, respectively, wherein the numbers of the specific pulses contained in the cam pulse signal during the first, second, third and fourth subperiods, respectively, should be xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d, xe2x80x9c2xe2x80x9d and xe2x80x9c0xe2x80x9d; xe2x80x9c1xe2x80x9d, xe2x80x9c2xe2x80x9d, xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d; xe2x80x9c1xe2x80x9d, xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the sequential order in which the individual cylinders are controlled.
With the arrangement described above, the angle of rotation required for cylinder identification of the three-cylinder engine can be decreased, whereby engine operation controllability can be enhance.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.